Serum vitamin C levels and risk of non-alcoholic fatty liver disease: results from a cross-sectional study and Mendelian randomization analysis

Antioxidants and the risk of metabolic dysfunction-associated steatotic liver disease: results of National Health and Nutrition Examination Survey and two-sample Mendelian randomization analyses

BACKGROUND

The link between antioxidants and metabolic dysfunction-associated steatotic liver disease (MASLD) is a topic of considerable discussion in the field of observational studies, with the exact causal connections still being unclear.

METHODS

In this investigation, a cohort consisting of 17 061 participants from the National Health and Nutrition Examination Surveys was studied. Initially, a cross-sectional analysis was carried out to examine the relationship between the CDAI and MASLD. Further, Mendelian randomization (MR) was utilized to assess the possible causal links between antioxidant levels in the bloodstream and MASLD.

RESULTS

The association between the CDAI and MASLD was found to be significant in the fully adjusted logistic regression model, showing an OR of 0.95 [95% confidence interval (CI): 0.94-0.97; P  < 0.001]. The use of restricted cubic spline regression revealed no significant nonlinear association between the CDAI and the occurrence of MASLD ( Pnonlinearity  = 0.321). Additionally, MR findings did not suggest any causal connections between circulating levels of various antioxidants and MASLD. These antioxidants included vitamin A (retinol) (IVW: OR: 0.67, 95% CI: 0.33-1.36, P  = 0.272), vitamin C (ascorbate) (IVW: OR: 0.61, 95% CI: 0.34-1.09, P  = 0.094), vitamin E (α-tocopherol) (IVW: OR: 0.55, 95% CI: 0.13-2.25, P  = 0.407), vitamin E (γ-tocopherol) (IVW: OR: 0.89, 95% CI: 0.36-2.23, P  = 0.806), zinc (IVW: OR: 0.95, 95% CI: 0.82-1.09, P  = 0.449), selenium (IVW: OR: 0.98, 95% CI: 0.84-1.16, P  = 0.855), and carotene (IVW: OR: 0.80, 95% CI: 0.36-1.81, P  = 0.596).

CONCLUSION

The findings highlight a significant negative linear relationship between CDAI and MASLD prevalence in the observational component of the study. However, the MR analysis did not indicate any causal effects of circulating antioxidant levels on MASLD.

The association between vitamin C and depressive risk based on the National Health and Nutrition Examination Survey of 2017-2018 and Mendelian randomization study

OBJECTIVES

There is some debate about the link between vitamin C and depressive risk. This study utilized data from the National Health and Nutrition Examination Survey (NHANES) and Mendelian randomization (MR) methodology to investigate the association between the two.

METHODS

We obtained serum vitamin C levels through laboratory data and determined the intake of vitamin C through a 24-hour dietary recall method on the first day from NHANES 2017 to 2018. Assessment of depressive risk was employed by the 9-item Patient Health Questionnaire (PHQ-9). The association between serum vitamin C levels and depressive risk was examined using logistic regression. Furthermore, the research utilized a two-sample MR methodology to investigate the potential causal connection between vitamin C and depressive risk.

RESULTS

Three thousand four hundred and thirty-four participants aged 20+ with serum vitamin C levels and depressive risk data was included. Among the participants, 18.7% had low serum vitamin C levels and 25.2% had self-reported depressive risk. Serum vitamin C levels were associated with depressive risk [OR 1.64, (95% CI: 1.36-1.97), P < 0.01], which remained significant [OR 1.32, (95% CI: 1.08-1.61), P < 0.01] after adjustments. Distinct genetic SNPs were identified for serum vitamin C levels and depressive risk, allowing detailed analysis. No additional influences were observed between genetic variations. IVW and MR Egger analysis showed a non-causal association between vitamin C levels and depressive risk (All P > 0.05).

CONCLUSIONS

Our findings of the nationally representative survey revealed a strong correlation between serum levels, intake as a supplement or medication of vitamin C and depressive risk, however, without a unidirectional causal association.

Molecular Pharmacology of Vitamin C and Relevance to Health and Obesity-A Narrative Review

The role of food constituents as pharmacological agents is an important consideration in health and obesity. Vitamin C acts as a small molecule antioxidant but is also a co-factor for numerous transition metal-dependent enzymes involved in healthy weight and energy metabolism. Vitamin C cannot be manufactured by humans and is mainly obtained from the dietary intake of fresh fruit and vegetables. There is great variability between different nutritional guidelines in the recommended daily allowance of vitamin C. Vitamin C deficiency results from an inadequate intake of vitamin C-containing foods and also increased utilization by oxidative and carbonyl stress. Risk factors for vitamin C deficiency include cigarette smoking, malnutrition, obesity, type 2 diabetes mellitus, age, race, sex, social isolation, major surgery, and Western-type diets. Despite the common belief that vitamin C deficiency is rare in affluent countries, surveys of large populations and specific patient groups suggest otherwise. Patients with obesity typically consume highly processed, energy-dense foods which contain inadequate micronutrients. As obesity increases, larger amounts of oral vitamin C are required to achieve adequate plasma and tissue concentrations, as compared to persons with a healthy weight. This is important in the control of oxidative stress and the maintenance of homeostasis and organ function. In this narrative review, the dosage, absorption, distribution, excretion, and catabolism of vitamin C are reviewed, together with the latest findings on vitamin C pharmacology in patients with obesity.

Fruit and vegetable intake and the risk of non-alcoholic fatty liver disease: a meta-analysis of observational studies

Purpose

This systematic review and meta-analysis of clinical observational studies aims to clarify the correlation between the intake levels of fruits and vegetables and non-alcoholic fatty liver disease (NAFLD).

Materials and methods

PubMed, Embase, Web of Science, and the Cochrane Library were searched for studies on the association between vegetable or fruit intake with the risk of NAFLD from the foundation of each database up until September 2023. The relative risk (OR) and the 95% confidence interval (CI) were pooled for both the highest and lowest consumption levels of vegetables and fruits to explore their association with the incidence of NAFLD.

Results

The meta-analysis encompassed 11 studies with a total of 493,682 patients. A higher consumption of vegetables (OR = 0.78, 95% CI = 0.67-0.91) and fruits (OR = 0.88, 95% CI = 0.83-0.93) was found to have a negative correlation with the risk of NAFLD, denoting an inverse association. This correlation, however, varied among different ethnic groups and gender.

Conclusions

Our results indicate that increased consumption of vegetables and fruits is associated with a reduced likelihood of developing NAFLD.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/#searchadvanced, identifier: CRD42023460430.

Associations of visual, hearing, and dual sensory impairment with motoric cognitive risk syndrome: Observational and Mendelian randomization analyses

BACKGROUND

Dementia is associated with individual vision impairment (VI) and hearing impairment (HI). However, little is known about their associations with motoric cognitive risk syndrome (MCR), a pre-dementia stage. We investigated the association of VI, HI, and dual sensory impairment (DSI) with MCR and to further evaluate causal relationships using Mendelian randomization (MR) approach.

METHODS

First, an observational study was conducted in the China Health and Retirement Longitudinal Study (CHARLS). Evaluate the cross-sectional and longitudinal associations of VI, HI, and DSI with MCR using the logistic regression models and Cox proportional hazard models, respectively. Second, evaluate the causal association between VI and HI with MCR using MR analysis. The GWAS data was used for genetic instruments, including 88,250 of European ancestry (43,877 cases and 44,373 controls) and 504,307 with "white British" ancestry (100,234 cases and 404,073 controls), respectively; MCR information was obtained from the GWAS with 22,593 individuals. Inverse variance weighted was the primary method and sensitivity analysis was used to evaluate the robustness of MR methods.

RESULTS

In the observational study, VI (HR: 1.767, 95%CI: 1.331-2.346; p < 0.001), HI (HR: 1.461, 95%CI: 1.196-1.783; p < 0.001), and DSI (HR: 1.507, 95%CI: 1.245-1.823; p < 0.001) were significantly associated with increased risk of MCR. For the MR, no causal relationship between VI (OR: 0.902, 95% CI: 0.593-1.372; p = 0.631) and HI (OR: 1.016, 95% CI: 0.989-1.043; p = 0.248) with MCR risk, which is consistent with the sensitivity analysis.

CONCLUSION

VI, HI, and DSI were significantly associated with MCR, but MR analysis failed to provide evidence of their causal relationship. Emphasized the importance of sensory impairment screening in identifying high-risk populations for dementia.